The thermal environment in clear and turbid water in the Darwin region of northern Australia in relation to the water seeding of rice

✍ Scribed by A.L. Chapman

• Publisher: Elsevier Science
• Year: 1969
• Weight: 698 KB
• Volume: 6
• Category: Article
• ISSN: 0002-1571
• DOI: 10.1016/0002-1571(69)90051-x

✦ Synopsis

Water seeding of rice in tropical Australia was simulated by sowing pregerminated seeds of 0. sativa L. cultivar Sircna in galvanized iron tanks on twelve occasions throughout an entire year. Individual tanks containing Adelaide River clay soil, were placed above ground and filled with a 10 or 30 cm depth of either clear water, clear water plus "OED" evaporation suppressant, or turbid water. The profiles of water and soil temperature were recorded continuously during the lo-day period following each sowing.

Total incoming short-wave radiation was recorded daily over a 3-year period and an estimate of net radiation over a water surface was made.

Mean temperature in 10 cm of clear water was 28-32°C from about mid September to mid May, and about 25°C during mid May to mid August. The temperature range was smaller in 30 cm of water, but mean temperature was approximately 1 "C higher. Evaporation suppression raised temperatures in all periods. Turbidity generally reduced temperatures.

Over the range 25-35°C seedling establishment decreased linearly with increasing mean temperature near the soil-water interface during the IO-day period following sowing. Seedling establishment in 30 cm of water was reduced to about one-half that in 10 cm of water. The evaporation suppressant reduced seedling establishment by an average of 18 % in 10 cm of water apparently due to its effect on temperature.

Turbidity had no effect on establishment.

The results are discussed in relation to water seeding of rice on the lower Adelaide River plains.